If the product of the integers r, s, t and u is 770, and if 1 < r< s< t< u, what is the value of r+ u?  Answers:
A) 10
B) 13
C) 16
D) 18
E) 21
770 = 2 * 5 * 7 * 11   So r= 2, s= 5, t= 7, u= 11   r+ u= 2 + 11= 
<gadget id="calculator">2 + 11</gadget>
<output>13</output>
13   Answer - 13
<result>B</result>
If the product of the integers r, s, t and u is 770, and if 1 < r< s< t< u, what is the value of r+ u?