Will give brainiest

evaluate the following expression when a=2 and b=5. show your work.
(2∙a)^(b-1)

evaluate the following expression when a=3 and b= -2. show your work.
〖7a〗^b

what is the order of the mass of electrons from least to greatest?
12.4 x 10-3, 14 x 102, 0.013 x 103, and 157 x 10-4
a. 12.4 x 〖10〗^(-3),14 x 〖10〗^2,0.013 x 〖10〗^3,157 x 〖10〗^(-4)
b. 12.4 x 〖10〗^(-3),157 x 〖10〗^(-4),14 x 〖10〗^2,0.013 x 〖10〗^3
c. 12.4 x 〖10〗^(-3),157 x 〖10〗^(-4),0.013 x 〖10〗^3,14 x 〖10〗^2
d. 0.013 x 〖10〗^3,12.4 x 〖10〗^(-3),157 x 〖10〗^(-4),14 x 〖10〗^2