Walter, a single taxpayer, purchased a limited partnership interest in a tax shelter in 1985. He also acquired a rental house in 2012, which he actively manages. During 2012, Walter's share of the partnership's losses was $30,000, and his rental house generated $20,000 in losses. Walter's modified adjusted gross income before passive losses is $120,000. 

a. Calculate the amount of Walter's allowable deduction for rental house activities for 2012. $__________

b. Calculate the amount of Walter's allowable deduction for the partnership losses for 2012. $________

c. What may be done with the unused losses, if anything? ______________________________