Find the radius of a circle with a circumference of 35 pie yards

For problems 29 - 31 the graph of a quadratic function y=ax^2 + bx + c is shown. tell whether the discriminant of ax^2 + bx + c = 0 is positive, negative, or zero.

Extra points! find the missing dimension! need asap

If a company produces x units of an item at a cost of $35 apiece the function c=35x is a of the total production costs