Choose Layer > New > Solid.

In the Solid Settings dialog box, name the layer Reflection, click the Make Comp Size button, change the Color to white, and then click OK.

Instead of trying to exactly re-create the shape of the office_mask layer’s mask, it is easier to copy it to the Reflection layer.

Select the office_mask layer in the Timeline panel and press the M key to display the Mask Path property for the mask.

Select Mask 1, and then choose Edit > Copy or press Ctrl+C (Windows) or Command+C (Mac OS).

Select the Reflection layer in the Timeline panel, and then choose Edit > Paste or press Ctrl+V (Windows) or Command+V (Mac OS).

This time, you want to keep the area inside the mask opaque and make the area outside the mask transparent.

Select the office_mask layer, and then press U to hide the mask properties.

Select the Reflection layer in the Timeline panel and press the M key to reveal the Mask 1 Mask Path property for the layer.

Deselect the Inverted option. The Reflection layer now obscures the news_promo layer.

Zoom in to see the screen, and then select the Selection tool (). In the Composition panel, select the lower-right vertex of the Reflection layer’s mask and drag it toward the upper-left corner of the mask.

Adjust the other vertices and direction handles until your shape resembles the following figure.

With the Reflection layer selected in the Timeline panel, press the F key to display the Mask Feather property for the mask.

Increase the Feather amount to 90, 90 pixels.

This creates an apparent reflection on the monitor, but because of the layers’ stacking order, the reflection spills onto the whole shot.

Select the Reflection layer in the Timeline panel and drag it below the office_mask layer.

With the Reflection layer selected, press T to reveal its Opacity property.

Reduce the Opacity value to 65% to reduce the intensity of the reflection.

Press T to hide the Opacity property, and then press F2 to deselect all layers.