In the following equations, t represents time in hours and m represents mass in mf. Which of them (if any) would have a mass less than 50 mg after 2 hours? Select all that apply.

a. y= 100(0.5)^x
b. y= 500 (0.3)^x
c. y= 80(2)^x
d. y=10(1.2)^x
e. y=30(1.5)^x
f. y=80(0.2)^x
g. y=100(2)^x