I would personally use 'd', though 'b' sounds fine, if not a little more formal.
'Ink' can be countable if we're talking about types of ink. Cambridge gives the example...
"The book is printed in three different coloured inks."
This happens with a lot of nouns that you might think of as uncountable. Off the top of my head...
"They have a wide selection of juices"
"Their soups are excellent."
"The peoples of the world came together."
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