A science teacher needs up to 15 female and male students for a competition. The science teacher needs at least 6 male volunteers. Let x represent the number of male volunteers and y represent the number of female volunteers. Which inequalities model the situation? Select each correct answer.
 a. x+y≤15 
 b. y≥0
 c. x+y<15
 d. x>6
 e. x≥6