Answer:
Therefore the  95% confidence interval is (25,707.480 < E < 26,744.920)
Step-by-step explanation:
n = 77
mean u = 26,226.2  bushels per acre
standard deviation s = 2,322.32
let E = true mean 
let A = test statistic
Find 95% Confidence Interval
so 
let  A =  (u - E) *  ( / s)   be the test statistic
  / s)   be the test statistic 
we want      P( average_l <  A  < average_u )  = 95%
look for  lower 2.5%  and the upper 97.5%  Because I think this is a 2-tail test
average_l =  -1.96  which corresponds to the 2.5%
average_u = 1.96
P(  -1.96  <  A  <  1.96)  =  95%
P(  -1.96  <  (u - E) *  ( / s)  <  1.96)  =  95%
  / s)  <  1.96)  =  95%
Solve for the true mean E ok
E   <   u + 1.96* (s  /  )
)
from  -1.96  <  (u - E) *  ( / s)
  / s)
E < 26,226.2 +  1.96*( 2,322.32 /  )
 )
E < 26,226.2 +  1.96*( 2,322.32 /  )
 )
E < 26,226.2 +  518.7197348105429466
upper bound is 26,744.9197
or
u - 1.96* (s  /  )  < E
)  < E
26,226.2 -  518.7197348105429466  < E
25,707.48026519  < E
lower bound is 25,707.48026519
Therefore the  95% confidence interval is (25,707.480 < E < 26,744.920)