The C(x) equation is a parabola with a squared "x" and a positive leading term coefficient, meaning, is a vertical parabola and it opens upwards
the lowest point, or lowest cost value, it reaches, is the U-turn point, or vertex

so, the lowest cost is at
C=-2 because you would transfer to the other side making it negative. It can't be a negative so you divide -1 to 2. Making it -2.
Answer:
75%
Step-by-step explanation:
Sorry if wrong >.<
she swims .625 laps per minute