Taking your 99% effectiveness of the pill, the probability of the failure of that is 1%, or 0.01. The probability of failure of the pull-out method (done correctly) is 4%, or 0.04. Combining the two, means the probability of simultaneous failure is 0.01*0.04 = 0.0004, or 0.04%, or 1 out of 2500 times.
This is in the form of retinal activity equivalents to account for the various sources of vitamin A. The best sources of preformed vitamin A are in liver and fish oils. This includes beef, calf, chicken liver and cod liver oil.
66% of all vitamin A intake in the American diet comes from retinol or preformed vitamin A added to foods (mostly as retinyl palmitate). Vitamin A is also found in supplements (as retinyl palmitate and retinyl acetate). Tolerable upper limit: 10,000 IU daily (see more below).