Roger's Utility Function Is U = Min{a₁, A₂} Min{b₁, B₂}

Multiple Choice

Roger's utility function is U = min{a₁, a₂} min{b₁, b₂}, where a₁ and a₂ are the number of piano lessons he consumes this year and next and b₁ and b₂ are the number of ice skating lessons he consumes this year and next. The price of piano lessons is $10 each and the price of ice skating lessons is $4 each. The prices won't change, but the interest rate is 7%. If Roger consumes 20 piano lessons this year, how many ice-skating lessons will he consume next year?

A) 50
B) 20
C) 40
D) 30
E) There is not enough information to be able to tell.