context: ###List of Questions
  (1) Convert 56.3788 seconds to microseconds.
  (2) What is prob of picking 3 u and 1 c when four letters picked without replacement from {n: 2, c: 4, t: 3, u: 3, x: 7}?
  (3) Suppose -44 = -2*q + 2*o - 0*o, 38 = 2*q - 4*o. Suppose -m + 37 = 2*h, -q = -4*m - m. Solve -6*f = -2*f - h for f.
  (4) Suppose -23 = -2*r + r. What is the units digit of r?
  (5) 5*-483
q_1: (1) Convert 56.3788 seconds to microseconds.
q_2: (2) What is prob of picking 3 u and 1 c when four letters picked without replacement from {n: 2, c: 4, t: 3, u: 3, x: 7}?
q_3: (3) Suppose -44 = -2*q + 2*o - 0*o, 38 = 2*q - 4*o. Suppose -m + 37 = 2*h, -q = -4*m - m. Solve -6*f = -2*f - h for f.
q_4: (4) Suppose -23 = -2*r + r. What is the units digit of r?
q_5: (5) 5*-483