Part 1) what is the length of cf
we know that
When two chords intersect each other inside a circle, the products of their segments are equal.
so
BF*FE=CF*FD-----> CF=BF*FE/FD-----> CF=7*17/14----> CF=8.5
the answer Part 1) is
A 8.5
Part 2) what is the length of ac
we know that
If two secant segments are drawn to a circle from an exterior point, then the product of the measures of one secant segment and its external secant segment is equal to the product of the measures of the other secant segment and its external secant segment
so
AC*BC=EC*DC-------> AC=EC*DC/BC----> AC=12*5/6----> AC=10
the answer Part 2) is
the option B. 10