If a+b+c=13, a2+b2+c2=69, then find ab+bc+ca Options:
A) 50
B) 30
C) 20
D) 94
E) 25
(a+b+c)2= a2+b2+c2+2(ab+bc+ca)   2(ab+bc+ca)= (a+b+c)2- a2+b2+c2   =169-69= 
<gadget id="calculator">169-69</gadget>
<output>100</output>
100   ab+bc+ca=50   50NSWER 50 50
<result>A</result>
If a+b+c=13, a2+b2+c2=69, then find ab+bc+ca