Half life is the time taken by a radioactive element to decay by half its original amount. Therefore, since half life of carbon-14 is 5700 years, then it would take 5700 years for a sample of carbon-14 to decay by half of its original amount.
Using the formula;
New mass = Original mass × (1/2)^n, where n is the number of half lives.
n = Period taken/Half life = 6350 years/5700 years =1.114
Therefore;
New mass = 11.24 × (1/2)^1.114
= 5.193 g
Hence, a mass of 5.193 g of Carbon-14 would remain after 6350 years.
