Evaluate the expression 64^-4/3

What are the angle measures in triangle abc? m∠a = 90°,  m∠b = 30°,  m∠c = 60°m∠a = 60°,  m∠b = 90°,  m∠c = 30°m∠a = 90°,  m∠b = 60°,  m∠c = 30°m∠a = 60°,  m∠b = 30°,  m∠c = 90°