From the blog "Don Mansfield's Blog"

Assume that you are pricing a firm-fixed-price contract using cost analysis. The prospective contractor has included a contingency of $100,000 in its cost proposal of the type described at FAR 31.205-7(c)(1): There is a 90% chance that this contingency will occur. If it occurs, there's a 100% chance it will cost $100,000. The prospective contractor can take Precaution A, which will cost $50,000. If the contingency occurs, Precaution A would reduce the chance of the contingency costin