Consider mass A, B and C as one object
Use formula
Net force = ma
Weight-friction = ma
(1+1)g -4 = (1+1+1)a
16 = 3a
a = 5.33 ms^-2
Consider mass A
T1-4 = ma
T1 = 4+5.33 = 9.33N
Consider mass C
mg - T2 = ma
10-T2= 5.33
T2 = 4.67 N
This is the fastest method but not good for your understanding
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