With apologies to Dave (ez4u), but as you shall see, I couldn't resist.
This pair of problems comes from a game between Takagawa and Fujisawa Hideyuki (GoGoD 1965-03-11a, 5.5 komi. Takagawa was White). I don't have to worry about whether the human play is textbook or not. These two guys, known as masters of the fuseki in their time, wrote the textbooks.
Problem 4.
Lots of choices, but I think that the bots will probably agree on the same point or next to it. And that they won't like Takagawa's play, by comparison.
Problem 5 is hidden, for when you are ready.
As the mainline variation shows, the top left is non-urgent.
aims to make two enclosures or to get the mutually desired extension at 
.
in the game. 
induces 
which induces 
; if next Black encloses the lower right, both have an ideal extension, so 
encloses the other corner and White approaches the lower right. This looks too good for White, so Black will probably play elsewhere with 
is a mistake worth several % in winrate and a few tenths of a point. I was surprised that GoGoD has 137 examples of this fuseki. The normal human continuation has been to simply enclose the upper right, mainly making the small knight shimari. Katago calculates that this is around 5% worse than playing b at the 3-3 point in the lower left. The approach at 
is the second most popular idea in human play. However, there are only two games with Black replying to 
with 
. Instead Black more often initiates some form of the nadare joseki with c in place of 
, Black should switch to b in the lower left. The difference is not large but Black is still better of by being the first to play there. When Black connects instead, White would be better off to enclose the bottom left and when White extends at the top instead, Black should take the last opportunity to invade.