Please explain answer and thought process

An algorithm takes 0.4ms for input size 50 (this allows you to determine the constant c, which will be different in each case). What is the largest size of an input that can be solved in one hour if the run time of the algorithm is . . . ?

(a) c n

(b) c n log n (assuming base 2)

(c) c n³

(d) c 2³