13 is related to 44 following a certain logic. Following the same logic, 15 is related to 50. To which of the following is 21 related, following the same logic?

(NOTE: Operations should be performed on the whole numbers, without breaking down the numbers into its constituent digits. E.g. 13 – Operations on 13 such as adding/subtracting/multiplying etc. to 13 can be performed. Breaking down 13 into 1 and 3 and then performing mathematical operations on 1 and 3 is not allowed.) ​​

13 is related to 44 

15 is related to 50 

21 is related ? 

Logic: Multiply the number by 3, then add 5.

For 13:
13 × 3 + 5 = 44

For 15:
15 × 3 + 5 = 50

For 21:
21 × 3 + 5 = 68

So, 21 is related to 68.

Thus, correct option is (a).