TypeScript: Park Service Volunteer Program

I’m stuck with this one TypeScript: Park Service Volunteer Program

import {
  RaccoonMeadowsVolunteers,
  RaccoonMeadowsActivity,
  raccoonMeadowsVolunteers,
} from './raccoon-meadows-log';

import {
  WolfPointVolunteers,
  WolfPointActivity,
  wolfPointVolunteers,
} from './wolf-point-log';

type CombinedActivity = RaccoonMeadowsActivity | WolfPointActivity;

type Volunteers = {
  id: number;
  name: string;
  activities: CombinedActivity[];
};

function combineVolunteers(
  volunteers: (RaccoonMeadowsVolunteers | WolfPointVolunteers)[]
) {
  return volunteers.map( volunteer => {
    let id
    id = volunteer.id
    if( typeof id === 'string'){
      id = parseInt(id, 10)
    }
    return {
      id: id,
      name: volunteer.name,
      activity: volunteer.activities
      }
  })
}

function isVerified( verified: string | boolean ){
  if( typeof verified === 'string'){
    return verified === 'Yes' ? true : false
  }
  return verified
}

function getHours(activity: CombinedActivity){
  if('hours' in activity){
    return activity.hours
  }else{
    return activity.time
  }
}

function calculateHours(volunteers: Volunteers[]) {
  return volunteers.map((volunteer) => {
    let hours = 0;

    volunteer.activities.forEach((activity) => {
      if (isVerified( activity.verified )){
        hours += getHours( activity )
      }
    });

    return {
      id: volunteer.id,
      name: volunteer.name,
      hours: hours,
    };
  });
}

const combinedVolunteers = combineVolunteers(
  [].concat(wolfPointVolunteers, raccoonMeadowsVolunteers)
);

console.log( combinedVolunteers )
const result = calculateHours( combinedVolunteers )
console.log( result )

I get the error on the second last line of my code:

index.ts:76:32 - error TS2345: Argument of type '{ id: any; name: string; activity: RaccoonMeadowsActivity[] | WolfPointActivity[]; }[]' is not assignable to parameter of type 'Volunteers[]'.
  Property 'activities' is missing in type '{ id: any; name: string; activity: RaccoonMeadowsActivity[] | WolfPointActivity[]; }' but required in type 'Volunteers'.

76 const result = calculateHours( combinedVolunteers )
                                  ~~~~~~~~~~~~~~~~~~

  index.ts:18:3
    18   activities: CombinedActivity[];
         ~~~~~~~~~~
    'activities' is declared here.


Found 1 error in index.ts:76

What’s wrong? Why don’t the two types of Volunteers not match?

I’ve figured it out:
I had two mistakes in my combineVolunteers function. This is correct:

function combineVolunteers(
  volunteers: (RaccoonMeadowsVolunteers | WolfPointVolunteers)[]
) {
  return volunteers.map( volunteer => {
    let id = volunteer.id
    if( typeof id === 'string'){
      id = parseInt(id, 10)
    }
    return {
      id: id,
      name: volunteer.name,
      activities: volunteer.activities
      }
  })
}