What is the meaning of a loan

Sam robinson borrowed $21,000 from a friend and promised to pay the loan in 10 equal annual installments beginning one year from the date of the loan. sam’s friend would like to be reimbursed for the time value of money at a 9% annual rate. what is the annual payment sam must make to pay back his friend?

Abc computer company has a $20 million factory in silicon valley in which in builds computer components. during the current year, abc's costs are labor (wages) of $1.01.0 million; interest on debt of $0.20.2 million; and taxes of $0.20.2 million. abc sells all its output to xyz supercomputer for $2.62.6 million. using abc's components, xyz builds four supercomputers at a cost of $0.8500.850 million each, which comes from $0.6500.650 million worth of components, $0.10.1 million in labor costs, and $0.10.1 million in taxes per computer. xyz has a $30 million factory. xyz sells three of the supercomputers to other businesses for $1.81.8 million each. at year's end, it had not sold the fourth. the unsold computer is carried on xyz's books as a $0.8500.850 million increase in inventory.

Rahm's credit card issuer calculates interest based on the outstanding balance at the end of the last billing period. what is this method of calculating interest on a credit card called?