Subject: Statistics - Regression hypotheses

[Question]
The local phone company assumes that the average number of daily 
phone calls goes up by 1.5 for each additional person in the 
household.  It has been suggested that people are more talkative 
than this.  A sample of 64 households was taken, and the slope of 
regression of Y (average number of daily phone calls) on X (size of 
household) was computed to be 1.75 with a standard error of the 
regression slope coefficient to be 0.25.  Test if significantly more 
calls per additional person are being made that the phone company 
assumes, using a level of significance of 0.10.  State explicit 
hypotheses and an explicit conclusion.

[Difficulty]
Am I on the right track?  What do they mean by "explicit"?  Am I 
missing anything?  Thanks!

[Thoughts]
Here is what I have come up with so far.

M=1.5, n=64, significance level=0.10

Y = Mx + c
y = 1.5 + c = 1.75
x = 0.25
y = 1.5 (0.25) + c = 1.75
1.5 (0.25) + c = 1.75
0.375 - 1.75 = c
-1.375 = c
y = 1.5x (.1375)

null hypothesis: Ho = 0.25
alternative hypothesis = H1 =/ 0.25