in$-$class exercise will test your practical understanding of the following.Proper NamingVariablesOperatorsType conversion CastingInstructions:$1.$ Ask the user to enter four numbers, three digits each!$2.$ Save each number as four separate string variables$\mathrm{.}3.$ Convert all string inputs into double variables$\mathrm{.}4.$ Add the first three numbers and store the result in an integer variable called"first Three."$5.$ Add all numbers and store the result in an integer variable called "totalSum"$6.$ Multiply the last two numbers and store the result in an integer variable called"lastTwo"$\mathrm{.}7.$ Add the variables "totalSum" and "lastTwo", saving the result as an integer variable$\mathrm{.}8.$ Subtract the fourth number from the "lastTwo" Variable.