CA foundation economics marginal product and total product

Nandan Gambhir (Student) (36 Points)

19 November 2020  
Suppose the first four units of a variable input generate corresponding total output of 150,200,350,550. What will be the marginal product of third unit of input ?
A) 50
B) 100
C) 150
D) 200
The answer given in the paper is 200, but i think the answer is 150, please explain !!