Answer:
using System.IO;
using System;
class Program
{
static void Main()
{
int credits, year;
string inputString;
double tuition;
const int LOWCREDITS = 12;
const int HIGHCREDITS = 18;
const double HOURFEE = 15000;
const double DISCOUNT = 0.15;
const double FLAT = 1900.00;
const double RATE = 100.00;
const int SENIORYEAR = 4;
Console.WriteLine("How many credits? ");
inputString = Console.ReadLine();
credits = Convert.ToInt32(inputString);
Console.WriteLine("Year in school? ");
inputString = Console.ReadLine();
year = Convert.ToInt32(inputString);
if(credits > LOWCREDITS)
tuition = HOURFEE * credits;
else if(credits == HIGHCREDITS)
tuition = FLAT;
else
tuition = FLAT + (credits - HIGHCREDITS) * RATE;
if(year < SENIORYEAR)
tuition = tuition - (tuition * DISCOUNT);
Console.WriteLine("For year {0}, with {1} credits",year, credits);
Console.WriteLine("Tuition is {0}", tuition.ToString("C"));
}