matching two expression

You have 2 unknowns, so you need 2 equations.

The best two equations in your case are:

a=2.47

b*t=0.0036*t

And have mathcad solve these simultaneously:

Success!
Luc

Hi. If c(t) is given, and you want to get a and b, can use the coeffs symbolic keyword, or evaluate c and c' at t=0.

Best regards.

Alvaro