I am using a calculator for this question so hopefully this helps + I added working out just in case.
a) mean - 124 (add them all together then divide by 25)
b) standard deviation - 7.776888838 (7.76 to d.p)
c) the person might have eaten foods that increase or decrease the BP so every time they took their blood pressure, it might not have been done as the same routine as others (if this makes sense). Also, some blood pressures are lower than others like for example some might go down to 110 but others go all the way up to like 132, does why I said that they might have eaten food or done activites that increases the blood pressure.
