Sum of the last value of a property

I have an event that may fire multiple times throughout a day per user.

The event has propertyY.

I want to sum the last/latest value of propertyX of the events for each unique propertyY day-by-day.

eg,​​
Day 1
event 1, propertyY=12, propertyX=40
event 2, propertyY=13, propertyX=50
event 3, propertyY=12, propertyX=60

Day 2
event 4, propertyY=12, propertyX=15
event 5, propertyY=13, propertyX=25
event 6, propertyY=13, propertyX=20

Day 1, sum of latest propertyX, per propertyY =  110
Day 2, sum of latest propertyX, per propertyY =  35