finish part R$4.2$ by $C++$

R$4\mathrm{.}2[2]$ Redeem Gifts

When such option is chosen, the system displays all the gifts under one of the Gift

Categories according to the user input choice of gift category. Fields about the gift records

should be displayed, including the Gift ID$,$ Gift Description, Price, Required Points $-$ the

actual required points for the customer, which could be a discounted value according to

the customer rank, see R$7.$ Gift records are sorted by the Required Points, from the

smallest to the largest. The display should also identify those gifts that the customer can

redeem by only using his available CC points without paying extra money.

The system then allows the user to enter the Gift ID of the gift that he wants to redeem,

followed by the amount of CC points used for redemption. For any invalid inputs $($e$.$g$.,$

wrong Gift ID$,$ out$-$of$-$range CC points for the redemption, etc.$),$ the system allows TWO

more retries. With more than THREE times of invalid inputs, the system prints an

appropriate error message and returns to the Customer View Menu.

The user can redeem a gift with "less$-$than$-$required" CC points through paying extra

money in the redemption transaction $($see R$7$ about the "Points Conversion Rule"$).$ As a

result, the user can still redeem a gift if his available CC points is less than the required one

for the gift.

After getting all user inputs, the system displays the extra money needed in the redemption

transaction and asks for the user's confirmation. Upon user's confirmation, the system

subtracts the correct amount of CC points from the Points Balance for the customer.

R$7$ Points Conversion Rule

The CC points of a customer could be modified by user operations under R$4.$ The change

should be made according to the "Points Conversion Rule" below, which also takes the

rank of the customer into consideration:

A spending of $$250$ can earn $1CC$ point. No CC point can be earned by the remaining

spending less than $$250.$

Conversion rate during gift redemption: $1CC$ point is worth $$0\mathrm{.}2.$

According to the rank of the customer, there is a discount on the CC points required for

a gift in the gift redemption. The final points required is rounded to nearest integer:

The rank of the customer does not affect the price of a gift.

During the redemption process, if the user redeems a gift using "less$-$than$-$required"

CC points, the extra money needed is calculated by subtracting the money value of the

$CC$ points used in the redemption $($calculated using the above conversation rate$)$ from

the price of the gift.

For example, consider a customer who is going to use $1600CC$ points to redeem gift

D$01$:

For a Gold customer:

Extra money needed $=$$$0$

$(1575$ CC points is required and to be deducted$)$