Sharon works for 5 hours to earn enough tips to buy an ice cream cake, while Karen works for 4. After how many hours will they be able to buy the cake together?	Choose the correct choice from the following options:
A) 1 hour  B) 2 hours  C) 3 hours  D) 4 hours  E) 5 hours
Sharon's earnings = 1/5 cake per hour   Karen's earnings = 1/4 cake per hour   Sharon + Karen's earnings= 9/20   They will be able to buy the cake in just over 2 hours   correct option is 3 hours
<result>C</result>
Sharon works for 5 hours to earn enough tips to buy an ice cream cake, while Karen works for 4. After how many hours will they be able to buy the cake together?