Which preconditions have to be fulfilled in the following exercise that i can apply a z-test and are they actually fulfilled? TIA

The Chief Executive Officer of Dunkley Distributors plc believes that 30 per cent of the firm’s orders come from first-time customers. A simple random sample of 100 orders will be used to estimate the proportion of first-time customers. What is the probability that the sample proportion P will be between 0.20 and 0.40?