Simphiwe, a student bought 50 memory sticks at R40 each for cash. All the memory sticks were marked to sell at R80 each. The sticks were sold for cash within 10 days, as follows: 40 were sold at R80...

Simphiwe, a student bought 50 memory sticks at R40 each for cash. All the memory sticks were marked to sell at R80 each. The sticks were sold for cash within 10 days, as follows: 40 were sold at R80 each, 6 at R75 each and 4 at R70 each. The gross percentage on sales (calculated to the nearest 2 decimal places) is?