f(x,y,z)=5sin(xyz), (a,b,c)=(1,1,π/4), and v⃗ =(3,-√2,3). Calculate the directional derivative of f at the point (a,b,c)=(1,1,π/4) in the direction defined by v⃗. Find the direction at (a,b,c)=(1,1,π/4) in which the rate of change of f is greatest. Find the maximum rate of change. Fill in the blank: f decreases the most at (a,b,c)=(1,1,π/4) in the direction of

f(x,y,z)=5sin(xyz), (a,b,c)=(1,1,π/4), and v⃗ =(3,-√2,3). 

1. Calculate the directional derivative of f at the point (a,b,c)=(1,1,π/4) in the direction defined by v⃗. 

2. Find the direction at (a,b,c)=(1,1,π/4) in which the rate of change of f is greatest.
3. Find the maximum rate of change. 
4. Fill in the blank: f decreases the most at (a,b,c)=(1,1,π/4) in the direction of