Constant costs with a backstop resources

Consider a resource that is to be used during two periods. In the first period, demand for the good is given by P1=100-Q1 and in the second period it is given by P2=140-Q2. There are 150 units of the good to be divided and it is available at zero cost. You may assume that the interest rate is 100%.

1. Find the efficient allocation. What is the price and quantity in each period?
   
2. Now calculate how the situation would change if a backstop were available at a cost of $30.