To solve this problem, we make use of the formula of combination.
 nCr = n! / r! (n – r)!
 where n is the total number of subject teachers and r is the number of subjects r = 1
  
 For the English class n = 3
 3C1 = 3! / 1! (3 – 1)! = 3
  
 For the Algebra class n = 4
 4C1 = 4! / 1! (4 – 1)! = 4
  
  
 For the Biology class n = 2
 2C1 = 2! / 1! (2 – 1)! = 2
  
 The total number of different schedules would be the product of the three combinations:
 total combinations possible = 3 * 4 * 2
 total combinations possible = 24