Problem $1$ is from the textbook exercise $3\mathrm{.}10\mathrm{.}3\mathrm{.}10($Invoice Class$)$ Create a class called Invoice that a hardware store might use to represent an invoice for an item sold at the stoe. An Invoice should include four data members$-$a part number $($type string$),$ a part description $($type string$),$ a quantity of the item being purchased $($type int$)$ and a price per item $($type int$).$ Your class should have a constructor that initializes the four data members. Provide a set and a get function for each data member. In addition, provide a member function named getInvoiceAmount that calculates the invoice amount i$.$e$.,$ multiplies the quantity by the price per item$),$ then returns the amount as an int value. If the quantity is not positive, it should be set to o$.$ If the price per item is not positive, it should be set to $0.$Write a test program that demonstrates class Invoice's capabilities.Task $1\mathrm{.}1$ address the requirements in above problem statement. The test program should follow the unit testing structure introduced at the lecture demos. $($A reference example is on the "Summary and reference" web page on Moodle.$)(20$ points$)$Incrementally$,$ we develop the Invoice class with the following extra specification.Task $1\mathrm{.}2$ add the copy constructor of class Invoice. $(5$ points$)$Task $1\mathrm{.}3$ add the destructor of class Invoice.$(5$ points$)$Task $1\mathrm{.}4$ define a public member function called clone$)$ that returns an Invoice object with the identical values of the current Invoice object. $(5$ points$)$Task $1\mathrm{.}5$ define a public member function with overloaded form of clone $($const Invoice & that returns an Invoice object with the identical values of the pass$-$by$-$referenceInvoice object. $(5$ points$)$Task $1\mathrm{.}6$ write a test program to demonstrates class Invoice's capabilities defined in