Rewrite the following loops without using the enhanced for loop construct. Here, values is an array of floating-point numbers.

a. for (double x : values) { total = total + x; }

b. for (double x : values) { if (x == target) { return true; } }

c. int i = 0;
for (double x : values) { values[i] = 2 * x; i++; }