Question 1012650
One key assumption is not known and that is whether the population is normally distributed. If you can assume that, then you would use a t-distribution, because you are estimating the sd using the sample sd.  If you don't know whether the population is normally distributed, a sample of 70 may be sufficient, but if the population were extremely skewed, even 70 might be insufficient.  Most people would probably invoke the Central Limit Theorem and say that 70 would be sufficient.  
Continuing, given the population is such that a sample of 70 may be considered adequate, 
t(0.975)=2.219
the interval is 2.219*0.05/sqrt (70)=0.0133
(1.2367,1.2633), or (1.24,1.26)