Solving for the global minimum variance portfolio

Question

Question: Assume there are 3 risky assets, A, B & C with the following expected returns, standard deviations of returns and correlation coefficients.

E (rA­)= 4%                    S.DEVA=5%                              rA, B=0.7

E (rB­)=5%                     S.DEVB=7%                               rA, C=-0.2

E (rC­) =15%                  S.DEVC=10%                             rB,C=0.3

Think about a world where there are no risk free assets, & just these 3 risky assets. Assume short sales are permitted. Answer for the weights and variance of the global minimum variance portfolio. If short sales are not permitted is the solution affected?