Does anybody know how to solve this question?

Question

a) Find the arc length function for the curve measured from the point P in the direction of increasing t from P and then reparametrize the curve with respect to arc length starting from P.

b) Find the point 4 units along the curve (in the direction of increasing t) from P.

r(t)=e^t sin(t)i+ e^t cos(t)j+ √(2e^t)k P(0,1, √2)

This is what I did for a). I will show b) later
r'(t)=e^t (cos(t)+sin(t))I+e^t (cos(t)-sin(t))+ e^t /√(2e^t)
lr'(t)l=√[(e^t (cos(t)+sin(t)))^2+(e^t (cos(t)-sin(t)))^2+ (e^t /√(2e^t))^2]
lr'(t)l=√[(e^2t +(cos^2 (t)+sin^2 (t))+ cos(t)+sin(t)+ e^2t (cos^2 (t)+sin^2 (t)) -cos(t)+sin(t)+ (e^2t) /2e^t]
lr'(t)l=√[e^2t + e^2t + (e^2t)/2e^t]
lr'(t)l=√[2e^2t + (e^2t)/2e^t]
lr'(t)l=√[(4e^3t)/2e^t + (e^2t)/2e^t]
lr'(t)l=√[(4e^3t +e^2t )/2e^t]
lr'(t)l=√[(2e^2t +(e^t )/2]
Fid I do it right and what next?