Assume the supply function of ice cream is written as: Qs = 100 + 20P - 10Pm, where Qs is the quantity supplied, P is price of ice cream, and Pm is the price of milk ($/gallon). If milk price increases by $2/gallon due to the policy change, how will the Qs change? Group of answer choices decreases by 10 increases by 20 increases by 10 decreases by 20.