r generate a column with random 1s and 0s with restrictions

I have a data set with 500 observations. I like to generate 1s and 0s randomly based on two scenarios

Current Dataset

  Id     Age    Category   
  1      23     1
  2      24     1
  3      21     2
  .      .      .
  .      .      .
  .      .      .
500      27     3

Scenario 1

• The total number of 1s should be 200 and they should be random. The remaining 300 should be 0s.

Scenario 2

• The total number of 1s should be 200. The remaining 300 should be 0s.
  • 40% of the 1s should be in Category1. That is 80 1s should be in Category1
  • 40% of the 1s should be in Category2 That is 80 1s should be in Category2
  • 20% of the 1s should be in Category3 That is 40 1s should be in Category3

Expected Output

  Id     Age    Category  Indicator  
  1      23     1         1
  2      24     1         0
  3      21     2         1
  .      .      .
  .      .      .
  .      .      .
500      27     3         1

I know function sample(c(0,1), 500) will generate 1s but I dont know how to make this generate 200 1s randomly. Also not sure how to generate 80 1s randomly in Category1, 80 1s in category2 and 40 1s in Category3.