An electric company calculates a person's monthly bill from the number of kilowatt-hours (kWh), x, used. The function b (x) = {0 . 1 0 x , x ≤ 2 0 0 0 . 1 5 ( x − 2 0 0 ) 2 0 , x > 2 0 0 b(x)How much is the bill for a person who uses 400 kWh in a month?A. 50B. 60C. 40D. 30