99. After nouns indicating a quantity or portion of some indefinite
whole, the substantive expressing that indefinite whole is preceded by
the preposition "da", of:
Estas skatolo da cxerizoj tie, there is a box of cherries there.
Mi trovis grandan sakon da mono, I found a large bag of money.
Li havas teleron da viando, he has a plate of meat.
Post horoj da gxojo ofte venas horoj da malgxojo,
after hours of joy there often come hours of sorrow.
100. The preposition "da" must not be used if a quantity or portion of a
"definite" or "limited" whole is expressed. If the word indicating the
whole is limited by "la", it is thereby made definite:
Telero de la maturaj pomoj, a plate of the ripe apples.
Sako de la bona kafo, a sack of the good coffee.