Joseki of the week 9

This week a 4-3 joseki is looked at where white plays a
high close approach, and black attaches underneath.
After the exchange of 4(c14) for 5(c16), white can choose between
a sold connection at a and the hanging connection at b.

After white plays a or b, black usually plays c but d is possible.

When using the sold connection, the joseki continues with
both players making extensions, ending in blacks sente.
White 3 can also be at a(d10).

When using the hanging connection, white can extend one extra space down the side.
However, white needs to be carefull of the weakness at a(c8).
b(b13) is the usual responce to an immediate invasion at a(c8) by black.

If there are any questions about the joseki of the week,
or if they are too basic, let us know in the comments!