A construction firm deals with lots of invoices. 20% of the all the invoices show amounts greater than $800. Imagine that the firm chooses a random sample of 50 invoices.

1. What is the mean of the sample proportion of invoices with amounts in excess of $800? Your answer should be between 0 and 1 with four digits after the period (e.g. 0.5612).

2. What is the standard error of the sample proportion of invoices with amounts in excess of $800? Your answer should be between 0 and 1 with four digits after the period (e.g. 0.5612).

3.What is the probability that more than 22.7% of these 50 invoices are for more than $800? Your answer should be between 0 and 1 with four digits after the period (e.g. 0.5612).

4. What is the probability that at least 25% of these 50 invoices are for more than $800? Your answer should be between 0 and 1 with four digits after the period (e.g. 0.5612).