$$2$$ dollars and $$30$$ cents + $$3$$ dollars and $$80$$ = $$6$$ dollars and $$10$$ cents 
Chris and Debbie want to buy the same book, but they do not take enough money. Chris needs $$2$$ dollars and $$30$$ cents more to buy that book. Debbie needs $$3$$ dollars and $$80$$ cents more to buy that book. The sum of their own money is equal to the price of the book. How much is the book? 
a. $$2$$ dollars and $$30$$ cents 
b. $$4$$ dollars and $$60$$ cents 
c. $$7$$ dollars and $$60$$ cents 
d. $$3$$ dollars and $$80$$ cents 
e. $$6$$ dollars and $$10$$ cents 