Three machines continuously process an unending number of jobs. The time it takes to process a job on machine A is a Uniform [0,4] random variable, the time it takes to process a job on machine B is Uniform [1,3] random variable, and the time it takes to process a job on machine C is an Exponential random variable with mean 2. What is the approximate probability together the 3 machines can process at least 90 jobs by time ?