The nth term from the end of an A.P., whose first term, last term and common difference are a, l and d respectively, is given by:

1. l + (n + 1)d

2. l − (n − 1)d

3. l + (n − 1)d

4. l − (n + 1)d

The sum of first 50 natural numbers is:

1. 1050

2. 1175

3. 1225

4. 1275