Remember molarity is defined by (moles/liters). We know the liters: 0.5 liters.
1. Convert 50ml into grams (we have the density)
2. Note that the problem says 62%w/w. This means 62% by weight. So only 62% of the grams you get here is and to account for this, we must multiply the mass we get by 0.62, and that is actually how many grams of sulfuric acid we have.
3. Convert grams to moles
4. Divide that number of moles by the liters (0.5) and you have your molarity.
P.S. The word stock is irrelevant.
Once these calculations have been done, I do get 0.96M