Sir. & Mrs. Once they are both 62, they file a joint return for 2016. They provide full support for their daughter who is 19, blind and has no income. their 21-year-old son is a full-time student and had $4,200 in income and provided 70 percent of his own support during 2016. 

How many exemptions can Mr. and Mrs. Vonce claim on their 2016 tax return?