Exponential graph

[catherine_mimi]

Hello~
I need some help determining the rule for a particular exponential graph
The question asks, 'Find the values of a and b such that the graph of y=ae^-bx goes through the points (3,50) and (6,10).
I have figured out that b= 1/3 log_e5 and that a=50e^log_e5, but how does a=250?
Thanks,
Catherine

[ikiwi]

e^loge5 = 5 (the e and the loge kind of cancel out)
a = 50 x 5 = 250