Lengthening the credit period effectively the price paid by the customer. Generally, this acts to sales.

1) the stages a new product goes through from beginning to end, i.e., the stages that a product passes through from introduction through growth, maturity, and decline. 2) the time from initial research and development to the time at which sales and support of the product to customers are withdrawn. 3) the period of time during which a product can be produced and marketed profitably.

                                          hope it

you have to put the parentheses like this:

in fact, you have to perform the operation inside parentheses first, and then proceed in order:

answer(d) all of the choices are correct;