Google-sheets – Complex Formula in Google Spreadsheet

I have a 'dashboard' sheet and a 'log' sheet. I'm trying to pull data from the 'log' sheet and perform calculations on the data before displaying it in the 'dashboard' sheet. The 'log' sheet will have several hundred rows of data. Inside of the log sheet is a column for 'Task' and I will be using the data in the 'Task' column to locate other data that is related to the specific task.

The Problem

I'm trying to locate all of the instances of a specific activity, gather the hours spent on the activity (1 column to left), and then add up the total time spent on the activity (all instances) before displaying the total in the 'dashboard' sheet.

I've done a little reading about the DSUM and ArraySum, but I really don't know where to start with this problem. I know I can create new sheets for every 'task', populate the individual sheets using a QUERY statement, perform the necessary calculations in the individual sheets, and then pull data into the dashboard sheet. But I'm wondering if there is a single formula that I can use to accomplish my goal.

Links

This is the document I'm working with.

Here is a video that explains the data needed and the problem I'm trying to solve.

Edit not from OP to include sections of two sheets:

log sheet

Dashboard sheet

The Dashboard sheet is after inclusion of a suggested formula in D36 and that copied up (ie part was not provided by OP).