One of the diagonals of a parallelogram is its altitude. what is the length of this altitude, if its perimeter is 50cm, and the length of one side is 1cm longer than the length of the other? pls include full proof tysm

 A
   ]  
   |
   |
   D                                |  B
                                      |
                                      |
                                       C

Let ABCD be this parallelogram 
AB + BC + CD + DA = 50, but AD = BC  and AB = DC, Then:
2.AD + 2.AB = 50 and :
AD+AB = 25 . We also know that AB+1 = AD (Given), then:
AD + (AD+1) = 25
2.AD = 24 
AD = 12, THEN AB = 12+1=13
Calculate DB the diagonal perpendicular to AD, using Pythagoras:

AD² + DB² = AB²
12² +DB² = 13²
DB² = 13² - 12² = 25
AND DB= 5

On monday,mrs.wise bought 3 lbs of apples at $4per lb= 4*3=$12on tuesday ,20%off and she buy 5 lbs of apples = $4-20%=3.20*5lb=$16example: other wise when she buy 5lbs on monday she have to spend 4*5=20

Ithink the answer is b.