Standard Brands Paint That Regularly Sells for $10 Per Gallon $\%$

Standard Brands paint that regularly sells for $10 per gallon is on sale for $8 per gallon.
a) What is the discount?
b) What is the discount rate?

A) a) $3; b) 20 $\%$
B) a) $2; b) 20 $\%$
C) a) $4; b) 30 $\%$
D) a) $2; b) 30 $\%$
E) a) $3; b) 30 $\%$