If the floating-point number representation on a certain system has a sign bit, a 3-bit exponent, and a 4-bit significand

a) What is the largest positive and the smallest positive number that can be stored on this system if the storage is normalized? (Assume that no bits are implied, there is no biasing, exponents use two’s complement notation, and exponents of all 0s and all 1s are allowed.) 

b) What bias should be used in the exponent if we prefer all exponents to be non-negative? Why would you choose this bias?