1. Use PT given in class to check whether the following expression is type correct. fn (y) -> (let val x-y in (y (fn (z) -> z)) end) Explain all steps clearly. 2. Use PT (extended) given in class to check whether the following expression is type correct. fn (y) -> (let fun f(x) -(x 2) in f(f (y)) end) Explainal steps clearly. 1. Use PT given in class to check whether the following expression is type correct. fn (y) -> (let val x-y in (y (fn (z) -> z)) end) Explain all steps clearly. 2. Use PT (extended) given in class to check whether the following expression is type correct. fn (y) -> (let fun f(x) -(x 2) in f(f (y)) end) Explainal steps clearly