The reliability function r(x) of an electronic component is the probability that the component continues to work for more than x days. Suppose that the working life of a component is measured by a random variable X with probability density function f(x).

a. Find a formula for r(x) in terms of f(x).

b. Suppose the working life (days) of a memory chip has an exponential distribution with a parameter λ = 1/2. Find r(10), the probability that the memory chip continues to work for more than 10 days.