Sal's gym holds a hot yoga class with space for 20 people. When the price is $4.50, the class fills up completely. Seeing the desire, Sal raises the...

Sal's gym holds a hot yoga class with space for 20 people.  When the price is $4.50, the class fills up completely.  Seeing the desire, Sal raises the price to $5.50.  But only 10 people come to the next class.  What is the price elasticity of demand for the hot yoga class? 

a) 0.20    b)0.50  c)  3.33   d) 2.50