If there are only two linear functions f and g which map [1,2] on [4,6] and in a ΔABC , c=f(1)+g(1) and a is the maximum value of r2 , where r is the distance of a variable point on the curve x2+y2−xy=10 from the origin, then sinA:sinC is
a. 1:2
b. 2:1
c. 1:1
d. None of these